The present invention relates to a technique of cleaning a substrate (a wafer) in semiconductor device fabrication or the like.
Semiconductor devices for use in networks or digital household electric appliances are desired to be further sophisticated and multifunctional, and to be low in power consumption. Accordingly, the trend toward micro-patterning for circuits is continuing. Together with the continuation of micro-patterning, a pattern collapse in the circuits has become a significant problem. In semiconductor device fabrication, a cleaning step is greatly used for the purpose of removing particles and metal impurities. As a result of this, the cleaning step occupies 30-40% of the whole of the semiconductor fabrication step. A phenomenon observed in the cleaning step when an aspect ratio of pattern is high due to the micro-patterning for semiconductor device is a pattern collapse, in which a gas-liquid interface that comes about collapses the pattern at the time of passing therethrough and at the time of drying the wafer after cleaning or rinsing.
In Patent Publication 1, there is disclosed a method of suppressing the pattern collapse, i.e., a technique of changing a cleaning liquid from water to 2-propanol before the gas-liquid interface passes through a pattern. However, this is said to have some constraints, for example, in that an adaptable aspect ratio of pattern is not higher than 5.
Additionally, Patent Publication 2 discloses a technique directed toward a resist pattern as a method of suppressing the pattern collapse. This is a method of decreasing a capillary force as far as possible thereby suppressing the pattern collapse.
However, the thus disclosed technique is directed toward the resist pattern and is for reforming a resist itself. Moreover, it can finally be removed together with the resist so as not to need to estimate a process of removing a treatment agent after drying. Therefore, this cannot be applied to the objects of the present invention.
Additionally, there is set forth in Patent Publication 3 a cleaning process for: conducting surface-reforming of a wafer surface formed having an uneven pattern with a film containing silicon, by oxidation or the like; forming a water-repellent protecting film on the surface by using a water-soluble surfactant or a silane coupling agent; reducing the capillary force; and preventing the pattern collapse.
Furthermore, in Patent Publications 4 and 5, there is disclosed a technique for preventing the pattern collapse by conducting a hydrophobicity-imparting treatment in the use of a treatment liquid containing: a silylation agent represented by N,N-dimethylaminotrimethylsilane; and a solvent.